METHOD OF THICKNESS CHANGING WORK FOR THIN PLATE

PURPOSE:To make the thickness changing work of thin plate easy and enable the improvement in working accuracy by using a vacuum adsorption disc in which a plurality of adsorption ports and a plurality of O-rings for dividing channels separately are disposed on a plurality of circumferential channel bottoms provided on the disc. CONSTITUTION:A vacuum adsorption disc for fixing a worked material 1 and keeping the flatness highly precisely has a plurality adsorption channels 3 circumferentially bored therein, which adsorption channels 3 are divided one another by O-rings 4 disposed in a ring form. Further, each adsorption channel 3 has a plurality of adsorption holes 5 communicated to each other on its chan nel bottom, and the adsorption holes 5 from a common passage, by which the holes are communicated to a vacuum pump. The vacuum adsorption disc body 2 is fixed on a rotary disc 7 by a chuck 6 of rotating machine and integrally rotated with it. A grinding cutting edge 8 disposed in the opposite position to the vacuum adsorption disc body 2 is installed on a fixed bed 9 and moved in the arrowed direction, and the worked material 1 is ground from the outer circumferential side to conduct the thickness changing process into a determined thickness distribution.